Mount structure for fuel cell stack

ABSTRACT

A mount structure for a fuel cell stack includes a first bracket member supporting and fixing the fuel cell stack to a first installation member, and a second bracket member supporting and fixing the fuel cell stack to a second installation member. A part of the second bracket includes a constricted portion having low strength in comparison with other portions of the second bracket member.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of co-pendingapplication Ser. No. 15/114,746, filed 27 Jul. 2016, which is a NationalPhase of International Application PCT/JP2015/051819, filed on Jan. 23,2015, which claims priority from three Japanese Patent Applications JP2014-017706, filed on Jan. 31, 2014, JP 2014-018983, filed on Feb. 4,2014, and JP 2014-230024, filed on Nov. 12, 2014. The entire disclosureof each of the discussed prior applications is incorporated herein byreference.

TECHNICAL FIELD

The present invention relates to a mount structure for fixing a fuelcell stack to a predetermined installation position.

BACKGROUND ART

For example, a solid polymer electrolyte fuel cell employs a membraneelectrode assembly (MEA) which includes an electrolyte membrane of apolymer ion exchange membrane, an anode provided on one side of theelectrolyte membrane, and a cathode provided on the other side of theelectrolyte membrane. The membrane electrode assembly is sandwichedbetween a pair of separators to form a power generation cell. In use, inthe fuel cell, generally, a predetermined number of power generationcells are stacked together to form a fuel cell stack, e.g., mounted in afuel cell vehicle (fuel cell electric vehicle, etc.).

In the fuel cell, a fuel gas flow field for supplying a fuel gas alongthe anode and an oxygen-containing gas flow field for supplying anoxygen-containing gas along the cathode are provided in the surfaces ofthe separators. Further, a coolant flow field for supplying a coolant isprovided between the adjacent separators along surfaces of the adjacentseparators.

In the fuel cell, so called internal manifold type fuel cell has beenadopted. In the internal manifold type fuel cell, fuel gas passages,oxygen-containing gas passages, and coolant passages extend through thefuel cells in the stacking direction for allowing the fuel gas, theoxygen-containing gas, and the coolant to flow through the fuel cell.The fuel gas passages (reactant gas passages) are a fuel gas supplypassage and a fuel gas discharge passage. The oxygen-containing gaspassages (reactant gas passages) are an oxygen-containing gas supplypassage and an oxygen-containing gas discharge passage. The coolantpassages are a coolant supply passage and a coolant discharge passage.In the fuel cell, at least one of the end plates is equipped with afluid manifold member connected to each passage for supplying ordischarging fluid (fuel gas, oxygen-containing gas, or coolant).

In the above in-vehicle fuel cell stack, various types of mountstructures for mounting the fuel cells in the vehicle have beenproposed, in order to protect the fuel cells and attach the fuel cellsto the vehicle. For example, an in-vehicle fuel cell disclosed inJapanese Laid-Open Patent Publication No. 2006-040753 and a fuel cellsystem for a movable body disclosed in Japanese Laid-Open PatentPublication 2004-127787 are known.

Further, in the in-vehicle fuel cell stack, it is necessary to suitablyprotect the fuel cells against external loads such as vibrations orimpacts during traveling of the vehicle. For example, a fuel cellinstallation structure disclosed in Japanese Laid-Open PatentPublication No. 2007-317406 is known. In this fuel cell installationstructure, a fuel cell stack formed by stacking a plurality of powergeneration cells is supported at an installation position using acushioning device. The cushioning device has a conversion function forconverting the direction of external force in a direction intersectingwith the stacking direction of the power generation cells of the fuelcell stack into the stacking direction of the power generation cells.

In the structure, when an external force is applied to the fuel cellstack in a direction perpendicular to the stacking direction of thepower generation cells, the direction of this external force isconverted into the stacking direction of the power generation cells inwhich the durability against the external force is relatively high.According to the disclosure, by this structure, improvement of thevibration resistance and impact resistance is achieved.

SUMMARY OF INVENTION

The cushioning device has a link mechanism between the installationsurface and each of both ends of the fuel cell stack, and thus, theentire installation structure has a considerably large size in thestacking direction of the fuel cell stack. Further, the structure iscomplicated, and uneconomical.

The present invention has been made to solve the problems of this type,and an object of the present invention is to provide a mount structurefor a fuel cell stack having a simple and economical structure whichmakes it possible to suitably protect the fuel cell stack against anexternal load.

According to the first aspect of the present invention, there isprovided a mount structure for fixing a fuel cell stack to a firstinstallation member and a second installation member that are providedas separate members. The fuel cell stack includes a plurality of fuelcells for generating electrical energy by electrochemical reactions of afuel gas and an oxygen-containing gas, the fuel cells being stackedtogether.

The mount structure includes a first bracket member configured tosupport the fuel cell stack and fix the fuel cell stack to the firstinstallation member, and a second bracket member configured to supportthe fuel cell stack and fix the fuel cell stack to the secondinstallation member. The second bracket member includes a constrictedportion having low strength in comparison with other portions of thesecond bracket member.

In the first aspect of the present invention, the mount member isattached to one of the end plates, and has a function of fixing the fuelcell stack to the installation position, and a function of covering thefluid manifold member to thereby protect the fluid manifold member.Therefore, it is not required to use a dedicated mount structure formounting the fuel cell stack and a dedicated protection structure forprotecting the fluid manifold member. Further, the mount member isattached to the end plate, and thus the mount member can also have afunction of reinforcing the strength of the end plate.

Accordingly, with the simple and economical structure, it becomespossible to suitably protect the fluid manifold member and reliably fixthe fuel cell stack to the installation position.

Further, in the first aspect of the present invention, when an externalload that is equal to or greater than a predetermined level is appliedto the fuel cell stack, the constricted portion of the second bracketmember is broken apart preferentially. Therefore, the fuel cell stack isnot bound with both of the first installation member and the secondinstallation member, which are provided as separate members. The fuelcell stack is separated from the second installation member, and theexternal load can be relieved reliably.

Accordingly, with the simple and economical structure, it becomespossible to suitably protect the fuel cell stack against the externalload.

According to the second aspect of the present invention, there isprovided a mount structure for fixing a fuel cell stack integrally to afirst installation member and a second installation member that areprovided as separate members. The fuel cell stack includes a pluralityof fuel cells for generating electrical energy by electrochemicalreactions of a fuel gas and an oxygen-containing gas, the fuel cellsbeing stacked together. The mount structure includes a first bracketmember configured to support the fuel cell stack and fix the fuel cellstack to the first installation member, and a second bracket memberconfigured to support the fuel cell stack and fix the fuel cell stack tothe second installation member. The second bracket member is fixed to alower surface of the fuel cell stack by a plurality of bolts insertablethrough a plurality of bolt holes formed in the second bracket member.The second bracket member further includes a cutout portion arrangedbetween the plurality of bolt holes adjacent to each other.

Further, in the second aspect of the present invention, when an externalload that is equal to or greater than a predetermined level is appliedto the fuel cell stack, the cutout portion formed at a part of thesecond bracket member is broken apart preferentially. Therefore, thefuel cell stack is not bound with both of the first installation memberand the second installation member, which are provided as separatemembers. The fuel cell stack is separated from the second installationmember, and the external load can be relieved reliably. Accordingly,with the simple and economical structure, it becomes possible tosuitably protect the fuel cell stack against the external load.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view schematically showing a fuel cell electric vehicleequipped with a fuel cell stack;

FIG. 2 is a partial exploded perspective view showing a casingcontaining the fuel cell stack;

FIG. 3 is an exploded perspective view showing main components of a fuelcell of the fuel cell stack;

FIG. 4 is a partial exploded perspective view showing a coolant manifoldmember of the fuel cell stack;

FIG. 5 is a partial exploded perspective view showing another fuel cellstack;

FIG. 6 is a side view showing a coolant manifold member of the fuel cellstack;

FIG. 7 is a side view schematically showing a front side of a fuel cellelectric vehicle equipped with a fuel cell stack to which a mountstructure according to an embodiment of the present invention isapplied;

FIG. 8 is a plan view schematically showing the fuel cell electricvehicle;

FIG. 9 is a perspective view showing a second bracket member of themount structure;

FIG. 10 is a view showing a state where the second bracket member isbroken due to application of an external load to the fuel cell electricvehicle;

FIG. 11 is a view showing a state where the fuel cell stack has movedfurther backward;

FIG. 12 is a side view schematically showing a front side of a fuel cellelectric vehicle equipped with a fuel cell stack to which a mountstructure according to another embodiment of the present invention isapplied;

FIG. 13 is a plan view schematically showing the fuel cell electricvehicle;

FIG. 14 is a perspective view from below showing a fuel cell stack towhich a mount structure according to yet another embodiment of thepresent invention is applied;

FIG. 15 is a plan view showing a second bracket member of the mountstructure shown in FIG. 14;

FIG. 16A is a view showing a first modification of the second bracketmember;

FIG. 16B is a view showing a second modification of the second bracketmember; and

FIG. 16C is a view showing a third modification of the second bracketmember.

DESCRIPTION OF EMBODIMENTS

As shown in FIG. 1, a fuel cell stack 10 is mounted in a front box (socalled, motor room) 12 f of a fuel cell electric vehicle (fuel cellvehicle) 12.

The fuel cell stack 10 includes a plurality of stacked fuel cells 14,and a casing 16 containing the fuel cells 14 (see FIGS. 1 and 2). Thecasing 16 may be provided as necessary. Alternatively, the casing 16 maynot be provided. As shown in FIG. 2, electrode surfaces of the fuelcells 14 are oriented upright, and the fuel cells 14 are stacked in avehicle width direction of the fuel cell electric vehicle 12 indicatedby an arrow B intersecting with a vehicle length direction (vehiclelongitudinal direction) thereof indicated by an arrow A.

As shown in FIG. 1, in the front box 12 f, first frame members(installation positions) 18R, 18L, which make up part of a vehicle bodyframe, extend in the direction indicated by the arrow A. The fuel cellstack 10 is mounted on the first frame members 18R, 18L. The fuel cellstack 10 may not be necessarily placed in the front box 12 f. Forexample, the fuel cell stack 10 may be placed under the vehicle floor atthe central portion of the vehicle, or adjacent to a rear trunk.

As shown in FIG. 2, at one end of the fuel cells 14 in the stackingdirection, a first terminal plate 20 a is provided. A first insulatingplate 22 a is provided outside the first terminal plate 20 a, and afirst end plate 24 a is provided outside the first insulating plate 22a. At the other end of the fuel cells 14 in the stacking direction, asecond terminal plate 20 b is provided. A second insulating plate 22 bis provided outside the second terminal plate 20 b, and a second endplate 24 b is provided outside the second insulating plate 22 b.

A first power output terminal 26 a extends outward from a substantiallycentral position (or a position deviated from the central position) ofthe laterally elongated (rectangular) first end plate 24 a. The firstpower output terminal 26 a is connected to the first terminal plate 20a. A second power output terminal 26 b extends outward from asubstantially central position of the laterally elongated (rectangular)second end plate 24 b. The second power output terminal 26 b isconnected to the second terminal plate 20 b.

Coupling bars 28 each having a fixed length are provided between thefirst end plate 24 a and the second end plate 24 b at central positionsof sides of the first end plate 24 a and the second end plate 24 b. Bothends of the coupling bars 28 are fixed respectively to the first endplate 24 a and the second end plate 24 b by screws 30 to apply atightening load to the stacked fuel cells 14 in the stacking directionindicated by the arrow B.

As shown in FIG. 3, the fuel cell 14 includes a membrane electrodeassembly 32 and a first metal separator 34 and a second metal separator36 sandwiching the membrane electrode assembly 32.

For example, the first metal separator 34 and the second metal separator36 are metal plates such as steel plates, stainless steel plates,aluminum plates, plated steel sheets, or metal plates havinganti-corrosive surfaces by surface treatment. The first metal separator34 and the second metal separator 36 have rectangular planar surfaces,and are formed by corrugating metal thin plates by press forming to havea corrugated shape in cross section and a wavy or serpentine shape onthe surface. Instead of the first metal separator 34 and the secondmetal separator 36, for example, carbon separators may be used.

The first metal separator 34 and the second metal separator 36 have alaterally elongated shape including long sides extending in a horizontaldirection indicated by the arrow A and short sides extending in agravity direction indicated by an arrow C. Alternatively, the shortsides may extend in the horizontal direction and the long sides mayextend in the gravity direction.

At one end of each of the fuel cells 14 in a long-side directionindicated by the arrow A, an oxygen-containing gas supply passage 38 aand a fuel gas supply passage 40 a are provided. The oxygen-containinggas supply passage 38 a and the fuel gas supply passage 40 a extendthrough the fuel cells 14 in the direction indicated by the arrow B. Anoxygen-containing gas is supplied to the fuel cells 14 through theoxygen-containing gas supply passage 38 a, and a fuel gas such as ahydrogen-containing gas is supplied to the fuel cells 14 through thefuel gas supply passage 40 a.

At the other end of each of the fuel cells 14 in the long-sidedirection, a fuel gas discharge passage 40 b and an oxygen-containinggas discharge passage 38 b are provided. The fuel gas discharge passage40 b and the oxygen-containing gas discharge passage 38 b extend throughthe fuel cells 14 in the direction indicated by the arrow B. The fuelgas is discharged from the fuel cells 14 through the fuel gas dischargepassage 40 b, and the oxygen-containing gas is discharged from the fuelcells 14 through the oxygen-containing gas discharge passage 38 b.

At opposite end portions of the fuel cell 14 in the short-side directionindicated by the arrow C, two coolant supply passages 42 a are providedon one side (i.e., on one end side in the horizontal direction), i.e.,on a side closer to the oxygen-containing gas supply passage 38 a andthe fuel gas supply passage 40 a. The two coolant supply passages 42 aextend through the fuel cells 14 in the direction indicated by the arrowB in order to supply a coolant. The coolant supply passages 42 a areprovided respectively on upper and lower opposite sides. At opposite endportions of the fuel cell 14 in the short-side direction, two coolantdischarge passages 42 b are provided on the other side (i.e., on theother end side in the horizontal direction), i.e., on a side closer tothe fuel gas discharge passage 40 b and the oxygen-containing gasdischarge passage 38 b. The two coolant discharge passages 42 b extendthrough the fuel cells 14 in the direction indicated by the arrow B inorder to discharge the coolant. The coolant discharge passages 42 b areprovided respectively on upper and lower opposite sides.

The membrane electrode assembly 32 includes a cathode 46 and an anode48, and a solid polymer electrolyte membrane 44 interposed between thecathode 46 and the anode 48. The solid polymer electrolyte membrane 44is formed by impregnating a thin membrane of perfluorosulfonic acid withwater, for example.

Each of the cathode 46 and the anode 48 has a gas diffusion layer (notshown) such as a carbon paper or the like, and an electrode catalystlayer (not shown) of platinum alloy supported on porous carbonparticles. The carbon particles are deposited uniformly on the surfaceof the gas diffusion layer. The electrode catalyst layer of the cathode46 and the electrode catalyst layer of the anode 48 are formed on bothsurfaces of the solid polymer electrolyte membrane 44, respectively.

The first metal separator 34 has an oxygen-containing gas flow field 50on its surface 34 a facing the membrane electrode assembly 32. Theoxygen-containing gas flow field 50 is connected to theoxygen-containing gas supply passage 38 a and the oxygen-containing gasdischarge passage 38 b. The oxygen-containing gas flow field 50 includesa plurality of wavy flow grooves (or straight flow grooves) extending inthe direction indicated by the arrow A.

The second metal separator 36 has a fuel gas flow field 52 on itssurface 36 a facing the membrane electrode assembly 32. The fuel gasflow field 52 is connected to the fuel gas supply passage 40 a and thefuel gas discharge passage 40 b. The fuel gas flow field 52 includes aplurality of wavy flow grooves (or straight flow grooves) extending inthe direction indicated by the arrow A.

A coolant flow field 54 is formed between the adjacent first and secondmetal separators 34, 36, i.e., between a surface 36 b of the secondmetal separator 36 and a surface 34 b of the first metal separator 34.The coolant flow field 54 is connected to the coolant supply passages 42a and the coolant discharge passages 42 b. The coolant flow field 54extends in the horizontal direction, and in the coolant flow field 54,the coolant flows over the electrode area of the membrane electrodeassembly 32.

A first seal member 56 is formed integrally with the surfaces 34 a, 34 bof the first metal separator 34, around the outer circumferential end ofthe first metal separator 34. A second seal member 58 is formedintegrally with the surfaces 36 a, 36 b of the second metal separator36, around the outer circumferential end of the second metal separator36.

Each of the first seal member 56 and the second seal member 58 is anelastic seal member which is made of seal material, cushion material,packing material, or the like, such as an EPDM, an NBR, a fluoro rubber,a silicone rubber, a fluorosilicone rubber, a butyl rubber, a naturalrubber, a styrene rubber, a chloroprene rubber, an acrylic rubber, orthe like.

As shown in FIG. 2, an oxygen-containing gas supply manifold member 60a, an oxygen-containing gas discharge manifold member 60 b, a fuel gassupply manifold member 62 a, and a fuel gas discharge manifold member 62b are connected to the first end plate 24 a. The oxygen-containing gassupply manifold member 60 a is connected to the oxygen-containing gassupply passage 38 a, the oxygen-containing gas discharge manifold member60 b is connected to the oxygen-containing gas discharge passage 38 b,the fuel gas supply manifold member 62 a is connected to the fuel gassupply passage 40 a, and the fuel gas discharge manifold member 62 b isconnected to the fuel gas discharge passage 40 b.

As shown in FIGS. 1 and 2, a mount member 64 is placed on the first endplate 24 a. The mount member 64 fixes the fuel cell stack 10 to thefirst frame member 18L. The mount member 64 is a bent plate memberhaving an L-shape in cross section. A plurality of holes 68 a are formedin a vertical surface 64 a of the mount member 64. The mount member 64is fixed to a lower central portion of the first end plate 24 a byscrews 66 being inserted into the holes 68 a. A plurality of holes 68 bare formed in a horizontal surface 64 b of the mount member 64. Screws70 are inserted through the holes 68 b, and screwed into screw holes(not shown) of the first frame member 18L.

As shown in FIG. 4, a coolant supply manifold member (fluid manifoldmember) (coolant manifold member) 72 a made of resin is attached to thesecond end plate 24 b. The coolant supply manifold member 72 a isconnected to the pair of coolant supply passages 42 a. A coolantdischarge manifold member (fluid manifold member) (coolant manifoldmember) 72 b made of resin is attached to the second end plate 24 b. Thecoolant discharge manifold member 72 b is connected to the pair ofcoolant discharge passages 42 b.

The coolant supply manifold member 72 a has upper and lower flanges 74 aconnected respectively to the upper and lower coolant supply passages 42a. The flanges 74 a are formed integrally with a supply main body part76 a. An inlet pipe 78 a is connected to an intermediate position of thesupply main body part 76 a. The flanges 74 a are fixed to the second endplate 24 b by screws 66, respectively.

The coolant discharge manifold member 72 b has upper and lower flanges74 b connected to the upper and lower coolant discharge passages 42 b.The flanges 74 b are formed integrally with a discharge main body part76 b. An outlet pipe 78 b is connected to an intermediate position ofthe discharge main body part 76 b. The flanges 74 b are fixed to thesecond end plate 24 b by screws 66, respectively.

A mount member 80 is placed on the second end plate 24 b. The mountmember 80 fixes the fuel cell stack 10 to the first frame member 18R,and covers the coolant discharge manifold member 72 b. The mount member80 has a cubic shape. The bottom of the mount member 80 facing thesecond end plate 24 b has a substantially rectangular shape.

A plurality of, e.g., three (or four), attachment portions 82 areprovided at the bottom of the mount member 80. Each of the attachmentportions 82 has a flat surface in parallel to the plate (flat) surfaceof the second end plate 24 b. The attachment portions 82 have respectiveholes 82 a extending in a horizontal direction, and the second end plate24 b has screw holes 84 corresponding to the holes 82 a. The screw holes84 are provided at upper and lower positions on an end of the second endplate 24 b that is closer to the coolant discharge manifold member 72 b,and provided at an upper position on an inner side relative to thecoolant discharge manifold member 72 b on the second end plate 24 b.Plates (or intermediate members) 83 may be interposed between theattachment portions 82 and the second end plate 24 b. It should be notedthat the plates (or intermediate members) 83 may be used for all of theattachment portions in second and subsequent embodiments describedlater.

A recess 85 is formed between the attachment portions 82, incorrespondence with the shape of the coolant discharge manifold member72 b, e.g., in correspondence with the shape of the outlet pipe 78 b.The recess 85 is provided as a cutout of the mount member 80 in order toavoid interference with the outlet pipe 78 b. Additionally, varioustypes of recess 85 may be provided between the attachment portions 82 incorrespondence with the shape of the coolant discharge manifold member72 b, e.g., in correspondence with the discharge main body part 76 b, ifnecessary.

A rectangular fixing portion 86 is provided at an end of the mountmember 80 opposite to the bottom of the mount member 80 (opposite to theend where the attachment portions 82 are present). A plurality of holes86 a are formed in the fixing portion 86 along the vertical direction. Aplurality of screw holes 88 are formed in the first frame member 18R incorrespondence with the holes 86 a.

Screws 90 are inserted through the holes 82 a, and screwed into thescrew holes 84 of the second end plate 24 b to thereby attach the mountmember 80 to the second end plate 24 b. Screws 92 are inserted throughthe holes 86 a, and screwed into the screw holes 88 of the first framemember 18R to thereby fix the mount member 80 to the first frame member18R.

As shown in FIG. 2, two sides (two faces) at both ends of the casing 16in the vehicle width direction indicated by the arrow B are the firstend plate 24 a and the second end plate 24 b. Two sides (two faces) atboth ends of the casing 16 in the vehicle length direction indicated bythe arrow A are a front side panel 96 and a rear side panel 98. Thefront side panel 96 and the rear side panel 98 are laterally elongatedplates. Two sides (two faces) at both ends of the casing 16 in thevehicle height direction indicated by the arrow C are an upper sidepanel 100 and a lower side panel 102. The upper side panel 100 and thelower side panel 102 are laterally elongated plates.

The front side panel 96, the rear side panel 98, the upper side panel100, and the lower side panel 102 are fixed to the first end plate 24 aand the second end plate 24 b using screws 108 screwed through holes 106into screw holes 104 formed on sides of the first end plate 24 a and thesecond end plate 24 b.

Hereinafter, operation of the fuel cell stack 10 will be describedbelow.

Firstly, as shown in FIG. 2, an oxygen-containing gas is supplied fromthe oxygen-containing gas supply manifold member 60 a at the first endplate 24 a to the oxygen-containing gas supply passage 38 a. A fuel gassuch as a hydrogen-containing gas is supplied from the fuel gas supplymanifold member 62 a at the first end plate 24 a to the fuel gas supplypassage 40 a.

Further, as shown in FIG. 4, a coolant such as pure water, ethyleneglycol, oil, or the like is supplied from the coolant supply manifoldmember 72 a at the second end plate 24 b to the pair of coolant supplypassages 42 a.

Thus, as shown in FIG. 3, the oxygen-containing gas flows from theoxygen-containing gas supply passage 38 a into the oxygen-containing gasflow field 50 of the first metal separator 34. The oxygen-containing gasflows along the oxygen-containing gas flow field 50 in the directionindicated by the arrow A, and the oxygen-containing gas is supplied tothe cathode 46 of the membrane electrode assembly 32 for inducing anelectrochemical reaction at the cathode 46.

In the meanwhile, the fuel gas is supplied from the fuel gas supplypassage 40 a to the fuel gas flow field 52 of the second metal separator36. The fuel gas moves along the fuel gas flow field 52 in the directionindicated by the arrow A, and the fuel gas is supplied to the anode 48of the membrane electrode assembly 32 for inducing an electrochemicalreaction at the anode 48.

Thus, in the membrane electrode assembly 32, the oxygen-containing gassupplied to the cathode 46 and the fuel gas supplied to the anode 48 areconsumed in the electrochemical reactions at catalyst layers of thecathode 46 and the anode 48 for generating electricity.

Then, the oxygen-containing gas consumed at the cathode 46 of themembrane electrode assembly 32 is discharged along the oxygen-containinggas discharge passage 38 b in the direction indicated by the arrow B. Inthe meanwhile, the fuel gas consumed at the anode 48 of the membraneelectrode assembly 32 is discharged along the fuel gas discharge passage40 b in the direction indicated by the arrow B.

Further, the coolant supplied to the pair of coolant supply passages 42a flows into the coolant flow field 54 between the first metal separator34 and the second metal separator 36. The coolant temporarily flowsinward in the direction indicated by the arrow C, and then, the coolantmoves in the direction indicated by the arrow A for cooling the membraneelectrode assembly 32. After the coolant moves outward in the directionin the direction indicated by the arrow C, the coolant is dischargedalong the pair of coolant discharge passages 42 b in the directionindicated by the arrow B.

As described above, in the fuel cell electric vehicle 12, electricalenergy from the fuel cell stack 10 is supplied to a traction motor (notshown) for allowing traveling of the fuel cell electric vehicle 12. Atthis time, as shown in FIG. 1, when an external load F as an impact isapplied from the front side to the fuel cell electric vehicle 12backward in the vehicle length direction indicated by the arrow Ab, thefront portion of the fuel cell electric vehicle 12 tends to be deformedinward easily. Therefore, in particular, the coolant discharge manifoldmember 72 b which is positioned in front of the coolant supply manifoldmember 72 a tends to be damaged easily, and liquid junction in the fuelcell stack 10 may occur undesirably.

As shown in FIGS. 1 and 4, the mount member 80 is attached to the secondend plate 24 b. The mount member 80 fixes the fuel cell stack 10 to thefirst frame member 18R, and covers the coolant discharge manifold member72 b. That is, the mount member 80 has a function of fixing the fuelcell stack 10 to the first frame member 18R and a function of protectingthe coolant discharge manifold member 72 b.

Therefore, it is not required to use a dedicated mount structure formounting the fuel cell stack 10 and a dedicated protection structure forprotecting the coolant discharge manifold member 72 b. Further, sincethe mount member 80 is attached to the second end plate 24 b, the mountmember 80 has a function of reinforcing the strength of the second endplate 24 b. In the structure, reduction in the thickness of the secondend plate 24 b can be achieved easily.

Accordingly, with the simple and economical structure, it becomespossible to protect the coolant discharge manifold member 72 b suitably,and reliably fix the fuel cell stack 10 to the first frame member 18R,which is an installation position of the fuel cell stack 10,advantageously.

The mount member 80 is attached to the second end plate 24 b in a mannerto cover the coolant discharge manifold member 72 b. However, thepresent invention is not limited in this respect. For example, inaddition to the mount member 80 covering the coolant discharge manifoldmember 72 b, a mount member (not shown) covering the coolant supplymanifold member 72 a may be provided. Further, instead of the mountmember 64, a mount member covering a desired manifold member may beattached to the first end plate 24 a as well.

FIG. 5 is a partial exploded perspective view showing a fuel cell stack120. The constituent elements of the fuel cell stack 120 that areidentical to those of the fuel cell stack 10 are labeled with the samereference numerals, and detailed description thereof is omitted. Also inembodiments described later, the constituent elements that are identicalto those of the fuel cell stack 10 according to the first embodiment arelabeled with the same reference numerals, and detailed descriptionthereof is omitted.

As shown in FIGS. 5 and 6, the fuel cell stack 120 has a mount member122 attached to the second end plate 24 b. The mount member 122 fixesthe fuel cell stack 120 to the first frame member 18R, and covers bothof the coolant supply manifold member 72 a and the coolant dischargemanifold member 72 b altogether. The mount member 122 has a cubic shape,and the bottom of the mount member 122 facing the second end plate 24 bhas a substantially triangular shape (or substantially rectangularshape).

A plurality of, e.g., three (or four), attachment portions 124 areprovided at the bottom of the mount member 122. Each of the attachmentportions 124 has a flat surface in parallel to the plate (flat) surfaceof the second end plate 24 b. The attachment portions 124 haverespective holes 124 a extending in a horizontal direction, and thesecond end plate 24 b has screw holes 126 corresponding to the holes 124a. The screw holes 126 are provided at both of upper corners and at alower central position of the second end plate 24 b, outside the coolantsupply manifold member 72 a and the coolant discharge manifold member 72b.

A recess 128 is formed between the attachment portions 124, incorrespondence with the shapes of the coolant supply manifold member 72a and the coolant discharge manifold member 72 b. The recess 128 isprovided as a cutout of the mount member 122 in order to avoidinterference with the other parts.

A rectangular fixing portion 130 is provided at an end of the mountmember 122 opposite to the bottom of the mount member 122. A pluralityof holes 130 a are formed in the fixing portion 130. The holes 130 aextend in the vertical direction. A plurality of screw holes 132 areformed in the first frame member 18R in correspondence with the holes130 a. Screws 134 are inserted through the holes 124 a, and screwed intothe screw holes 126 of the second end plate 24 b to thereby attach themount member 122 to the second end plate 24 b. Screws 136 are insertedthrough the holes 130 a, and screwed into the screw holes 132 of thefirst frame member 18R to thereby fix the mount member 122 to the firstframe member 18R.

In the mount structure, the mount member 122 has a function of fixingthe fuel cell stack 120 to the first frame member 18R and a function ofprotecting both of the coolant supply manifold member 72 a and thecoolant discharge manifold member 72 b together. Accordingly, with thesimple and economical structure, the coolant supply manifold member 72 aand the coolant discharge manifold member 72 b are protected suitably.Further, it becomes possible to reliably fix the fuel cell stack 120 tothe first frame member 18R.

Although the second embodiment has been described only with regard tothe second end plate 24 b, the first end plate 24 a may have the samestructure as the second end plate 24 b.

As shown in FIGS. 7 and 8, a mount structure 140 according to anembodiment of the present invention is applied to a fuel cell stack 142.The fuel cell stack 142 is mounted in a front box 143 f of a fuel cellelectric vehicle 143.

The mount structure 140 includes first bracket members 144 a, 144 b. Thefirst bracket members 144 a, 144 b support the fuel cell stack 142, andare fixed to first frame members (first installation members) 18L, 18R.The first bracket members 144 a, 144 b have the same structure as themount member 64.

As shown in FIG. 7, the mount structure 140 includes a second bracketmember 148. In a state where the second bracket member 148 supports thefuel cell stack 142, the second bracket member 148 is fixed to a secondframe member (second installation member) 18SF of the vehicle framethrough a traction motor 146. The traction motor 146 can be driven byelectrical energy generated by the fuel cell stack 142, and the tractionmotor 146 is fixed to the second frame member 18SF through a first motorbracket 150 a by using screws. A second motor bracket 150 b is attachedto the traction motor 146, and the second motor bracket 150 b isconnected to the second bracket member 148.

As shown in FIGS. 7 to 9, the second bracket member 148 includes a flatportion 148 a coupled to a bottom portion of the fuel cell stack 142,more specifically, a substantially central portion of the lower sidepanel 102 in the direction indicated by the arrow B. As shown in FIG. 9,a plurality of, e.g., two, holes 152 a are formed in the flat portion148 a. Screws 154 are inserted through the holes 152 a, and screwed intoscrew holes (not shown) of the lower side panel 102 to thereby fix thesecond bracket member 148 to the lower side panel 102. The number ofholes 152 a is not limited to two, and can be determined depending onthe required joining strength.

A pair of support portions 148 b extend downward from the flat portion148 a, and each of the support portions 148 b is constricted in ahorizontal direction to form a constricted portion 148 bk. The thicknessof the constricted portion 148 bk is reduced in the horizontaldirection, and the strength of the constricted portion 148 bk isweakened only against the force applied backward in the horizontaldirection indicated by the arrow Ab. The strength of the constrictedportion 148 bk in the horizontal direction (shearing direction) is lowin comparison with the other portions of the second bracket member 148.The position of the constricted portion 148 bk is not limited to thethird embodiment. As long as the thickness in the horizontal directioncan be reduced, the constricted portion 148 bk may be provided at anyposition.

That is, the constricted portion 148 bk is configured to have a lowsection modulus in the longitudinal direction of the vehicle. Further,the constricted portion 148 bk may be configured to have a low sectionmodulus in the lateral direction of the vehicle. By adopting theconfiguration, if an impact is applied to the vehicle from the lateralside, the second bracket member 148 can be broken at the constrictedportion 148 bk suitably.

Legs 148 c extend from lower ends of the support portions 148 b,respectively. The legs 148 c are inclined downward from the horizontaldirection, and holes 152 b extending in the horizontal direction areformed in terminal end portions of the legs 148 c, respectively. Thesecond motor bracket 150 b is disposed between the legs 148 c. A hole156 is formed in the second motor bracket 150 b. A shaft 158 is insertedthrough the holes 152 b of the legs 148 c and the hole 156, and athreaded portion at the front end of the shaft 158 is screwed into a nut160. The second bracket member 148 and the second motor bracket 150 bare fixed together.

As shown in FIG. 7, a fuel cell cooling radiator 162 is provided on thesecond frame member 18SF. The fuel cell stack 142 is provided adjacentto the backside of the radiator 162.

Operation of the fuel cell stack 142 will be described below.

Electrical energy generated by the fuel cell stack 142 is supplied tothe traction motor 146 for allowing traveling of the fuel cell electricvehicle 143. At this time, as shown in FIG. 7, when an external load Fas an impact is applied from the front side to the fuel cell electricvehicle 143 backward in the vehicle length direction indicated by thearrow Ab, the front portion of the fuel cell electric vehicle 143 tendsto be deformed inward easily.

Therefore, as shown in FIG. 10, the radiator 162 moves backward in thedirection indicated by the arrow Ab, and abuts against the fuel cellstack 142. Therefore, a load is applied backward to the fuel cell stack142. In this regard, by the mount structure 140, the fuel cell stack 142is fixed to the first frame members 18R, 18L and the second frame member18SF, which are provided as separate members.

In the present embodiment, the second bracket member 148 of the mountstructure 140 includes the constricted portion 148 bk having lowstrength in comparison with the other portions (see FIG. 9). Morespecially, a pair of support portions 148 b extend downward from theflat portion 148 a, and each of the support portions 148 b isconstricted in the horizontal direction to form the constricted portion148 bk. The strength of the constricted portion 148 bk is weakened onlyagainst the force applied backward in the horizontal direction indicatedby the arrow Ab. The strength of the constricted portion 148 bk in thehorizontal direction (shearing direction) is low in comparison with theother portions of the second bracket member 148.

Therefore, when an external load F that is equal to or greater than apredetermined level is applied to the fuel cell stack 142 in thehorizontal direction, the constricted portion 148 bk of the secondbracket member 148 is broken apart preferentially. Therefore, the fuelcell stack 142 is not bound with all of the first frame members 18L, 18Rand the second frame member 18SF, which are provided as separatemembers. The fuel cell stack 142 is separated from the second framemember 18SF (see FIG. 10).

That is, the fuel cell stack 142 is supported only by the first framemembers 18L, 18R through the first bracket members 144 a, 144 b. In thestructure, it is possible to reliably relieve the external load Fwithout being affected by deformation of the second frame member 18SF.Thus, in the third embodiment, with the simple and economical structure,it becomes possible to suitably protect the fuel cell stack 142 againstthe external load F.

Further, in the present embodiment, the traction motor 146 is separatedfrom the fuel cell stack 142. Therefore, as shown in FIG. 11, thetraction motor 146 can move below the first frame members 18L, 18R. Inthe structure, it becomes possible to suitably suppress entry of thetraction motor 146 into, for example, an area around the braking pedal(not shown).

As shown in FIGS. 12 and 13, a mount structure 170 according to anotherembodiment of the present invention is applied to a fuel cell stack 142.The constituent elements that are identical to those of the mountstructure 140 are labeled with the same reference numerals, and detaileddescription thereof is omitted.

The mount structure 170 includes a motor mount 172 for fixing the rearside of the traction motor 146 to the second frame member 18SF. Themotor mount 172 includes a fuel cell fixing part 174 and a motor fixingpart 176, which are disposed respectively at upper and lower positionsthereof. Further, the motor mount 172 includes attachment portions 180a, 180 b, which are provided below the motor fixing part 176. Theattachment portions 180 a, 180 b are fixed to a cross frame 178 usingscrews.

As shown in FIG. 13, a pair of the attachment portions 180 a areprovided on the left and right sides. The attachment portion 180 b isprovided on an imaginary line S passing between the pair of attachmentportions 180 a in the width direction indicated by the arrow B. The pairof attachment portions 180 a and the attachment portion 180 b arearranged at positions corresponding to the corners of a triangular shapeT in a plan view. The cross frame 178 is fixed to a pair of the secondframe members 18SF.

As shown in FIG. 12, a pair of legs 148 c are fixed to the fuel cellfixing part 174 through rubber members (not shown) by use of screws, tothereby fix the second bracket member 148 to the motor mount 172. Thesecond motor bracket 150 b attached to the traction motor 146 is fixedto the motor fixing part 176 using a tightening pin 156 c.

The second bracket member 148 of the mount structure 170 has aconstricted portion 148 bk having a lower strength in comparison withthe other portions. Thus, with the simple and economical structure, thesame advantages as in the case of the mount structure 140 are obtained.For example, it becomes possible to suitably protect the fuel cell stack142 against the external load F.

As shown in FIG. 14, a second bracket member 192 of a mount structure190 according to yet another embodiment is fixed to a lower surface 142a (a lower surface of the casing 16) of a fuel cell stack 142 by aplurality of bolts 154. The mount structure 190 is equipped with firstbracket members 114 a, 144 b, as in the mount structures 140, 170 (see,for example, FIG. 7).

As shown in FIG. 15, the second bracket member 192 has a plurality(three in the illustration) of bolt holes 194 through which theplurality of bolts are inserted, and a cutout portion 196 arrangedbetween the plurality of bolt holes 194 adjacent to each other.

The second bracket member 192 includes a plate portion 192 a overlaid onand fixed to the lower surface 142 a (the lower surface of the casing16) of the fuel cell stack 142. The plate portion 192 a forms a base ofthe second bracket member 192 and fastened to the lower surface of thefuel cell stack 142 by the bolts 154. The plurality of bolt holes 194and the cutout portion 196 are formed in the plate portion 192 a.

As shown in FIGS. 14 and 15, the second bracket member 192 furtherincludes a pair of legs 192 b extending downward parallel to each otherfrom the plate portion 192 a to the rear side of the vehicle (in thedirection of arrow Ab). Each of the legs 192 b has a hole 193 formedrespectively therein for receiving a shaft portion of a bolttherethrough, where the holes 193 are coaxial and aligned with oneanother, and in this way, the second bracket member 192 is configured tobe attached to a second motor bracket 150 b of the traction motor 146.The pair of legs 192 b is separated from and opposed to each otherhorizontally (in the direction of arrow B). The second motor bracket 150b is disposed between the pair of legs 192 b (see FIG. 7). The pair oflegs 192 b are fixed to the second motor bracket 150 b by bolts 154 andnuts 160 (see FIG. 9).

As shown in FIG. 15, three bolt holes 194 are arranged at respectivevertices of an isosceles triangle. Two bolt holes 194 b, 194 c formed atpositions corresponding to respective ends of the base of the isoscelestriangle are separated from each other in the horizontal direction (thedirection of arrow B). The other bolt hole 194 a is formed closer to thefront side of the vehicle than the two bolt holes 194 b, 194 c describedabove.

In the plate portion 192 a, (thin-walled) depressions 198 (depressions198 a to 198 c) recessed from the other part of the plate portion 192 aare formed around the bolt holes 194. The depressions 198 are providedin the plate portion 192 a on a surface opposite to the surface facingthe lower surface 142 a of the fuel cell stack 142. The depressions 198are configured such that a thickness of the plate portion 192 a at thedepressions is less than a thickness of the plate portion at other partsthereof.

The cutout portion 196 has a groove structure. The cutout portion 196has lower strength in comparison with other portions of the secondbracket member 192. The cutout portion 196 is formed, for example, bymachining (cutting). In this case, it is possible to set a fracture loadbearing by adjusting the extent of machining. The cutout portion 196 maybe formed by forging, molding, or the like.

The cutout portion 196 extends straight along the (horizontal) direction(the direction of arrow B) in which the plurality of bolt holes 194adjacent to each other are separated. Specifically, the cutout portion196 is arranged between two bolt holes 194 b, 194 c positioned at therespective ends of the base of the isosceles triangle.

As viewed from the thickness direction (the direction of arrow C) of theplate portion 192 a, the cutout portion 196 is arranged along thestraight line L connecting the centers of the bolt holes 194 adjacent toeach other. One end of the cutout portion 196 communicates with thedepression 198 b surrounding the bolt hole 194 b. The other end of thecutout portion 196 communicates with the depression 198 c surroundingthe bolt hole 194 c.

In FIG. 14, the cutout portion 196 is formed at the positioncorresponding to the base of the isosceles triangle. The cutout portion196 is provided in the second bracket member 192 (the plate portion 192a) on a surface opposite to the surface facing the lower surface 142 aof the fuel cell stack 142. The cutout portion 196 is recessed towardthe lower surface 142 a of the fuel cell stack 142. The cutout portion196 may be provided in the second bracket member 192 (the plate portion192 a) on the surface facing the lower surface 142 a of the fuel cellstack 142.

According to the mount structure 190, the cutout portion 196 formed at apart of the second bracket member 192 is broken apart preferentially,when an external load that is equal to or greater than a predeterminedlevel is applied to the fuel cell stack 142. Therefore, the fuel cellstack 142 is not bound integrally with the first installation member(first frame members 18R, 18L) and the second installation member(second frame member 18FS), which are provided as separate members. Thefuel cell stack can be separated from the second installation member,and the external load can be relieved reliably. Accordingly, with thesimple and economical structure, it becomes possible to suitably protectthe fuel cell stack 142 against the external load.

The mount structure 190 may utilize second brackets 192A to 192C shownin FIGS. 16A to 16C instead of the second bracket 192 described above.

The second bracket 192A shown in FIG. 16A has one cutout portion 196between the bolt holes 194 a, 194 b formed at positions corresponding toboth ends of one side of the isosceles and another cutout portion 196between the bolt holes 194 a, 194 c at positions corresponding to bothends of the other side of the isosceles.

The second bracket 192B shown in FIG. 16B has bolt holes 194 atpositions corresponding to respective corners of a quadrangle. Among thefour bolt holes 194, the cutout portion 196 is formed between two boltholes 194 positioned on the front side of the vehicle (the direction ofarrow Af).

The second bracket 192C shown in FIG. 16C has bolt holes 194 atpositions corresponding to respective corners of a quadrangle. Among thefour bolt holes 194, the cutout portion 196 is formed between two boltholes 194 positioned on the rear side of the vehicle (the direction ofarrow Ab).

What is claimed is:
 1. A mount structure for fixing a fuel cell stack toa first installation member and a second installation member that areprovided as separate members, the fuel cell stack including a pluralityof fuel cells for generating electrical energy by electrochemicalreactions of a fuel gas and an oxygen-containing gas, the fuel cellsbeing stacked together, the mount structure comprising: a first bracketmember configured to support the fuel cell stack and fix the fuel cellstack to the first installation member; and a second bracket memberconfigured to support the fuel cell stack and fix the fuel cell stack tothe second installation member, wherein the second bracket member has aplate portion configured to be fixed to a lower surface of the fuel cellstack by a plurality of bolts, and wherein the plate portion has aplurality of bolt holes through which the plurality of bolts areinserted, and in the plate portion, on a side opposite to a sideconfigured to contact the lower surface of the fuel cell stack, each ofthe plurality of bolt holes has a depression extending therearound andconfigured such that a thickness of the plate portion at the depressionsis less than a thickness of the plate portion at other parts thereof,and wherein a cutout portion is formed in the plate portion and extendsstraight between two of the plurality of bolt holes adjacent to eachother along a direction in which said two of the plurality of bolt holesare separated from each other, and both ends of the cutout portion,respectively, are connected to the depressions surrounding said two ofthe plurality of bolt holes.
 2. The mount structure according to claim1, wherein the cutout portion is configured as a groove.
 3. The mountstructure according to claim 1, wherein the cutout portion is arrangedalong a straight line connecting centers of the plurality of bolt holesadjacent to each other, as viewed from a thickness direction of theplate portion.
 4. The mount structure according to claim 1, wherein theplurality of bolt holes are arranged at positions corresponding torespective vertices of an isosceles triangle, and the cutout portion isformed at a position corresponding to a base of the isosceles triangle.5. The mount structure according to claim 1, wherein the second bracketmember further comprises a pair of legs extending downwardly from theplate portion and spaced apart from one another, each of the legs havinga hole formed respectively therein for receiving a shaft portion of abolt therethrough, the holes being coaxial and aligned with one another.